Silver Dollars and Trade Dollars of the United States: A Complete Encyclopedia

by Q. David Bowers is now available in an online format over at PCGS.com.

This may be helpful for those trying to attribute their early bust dollars or seeking info on the workings of the early mint. It is not a very user friendly interface but, it is better than nothing (very similar to HA's hosting of Jules Reiver's identification manual for reeded edge half dollars).

http://www.pcgs.com/books/silver-dollars/